Contemplating the Interstellar Wars, when did the 1st Vargr reach the Solomani Rim?
During the Interstellar Wars 0%. With confidence on my part.
The Mongoose 1e Alien Modules regarding Vargr go into detail during this period. The Vargr discovered/invented Jump around -3810. The Vilani were still doing the Consolidation Wars at this time. Distance to the Vilani and the barrier that is the Windhorn Rift saved the Vargr from being discovered and taken over. Grandfather help them if they had been found and had Jump 2. They Vargr grew and expanded coreward and Spinward, but did not encounter the Vilani until around -2400 when Vargr found the end of the Rift in Corridor Sector, around the same time the Terrans appeared. From there, the raiding of Vilani worlds began.
At Jump 2, GURPS: IW said Imperial fleets took about 2 years to go from Vland to the Terrans. Since pirates and raiders were generally the first Vargr encountered, It's likely the Vilani did not let them pass. Despite the decline of the imperium, the Vilani still had enough strength to keep them from advancing fast. So if your Vargr made it past hostile Vilani navies, you still had a 2 year journey to get to Terra, longer if you only had Jump 1. Thru uncharted territory, which included even more Vilani bases.
Though there is no canon statement that says "There were no Vargr in the Rim", it just does not seem likely. Just like the Aslan. There were no Aslan in the Rim until at least -1999, when the Terran Cruiser crashed on their homeworld and they reverse engineered Jump Drive from it.
Sublight colonies? Not likely either. For comparison, look at how long the pre-Interstellar Wars Terran generation ships took to get to Reft Sector.